1. Field of the Invention
This invention relates to machine tools and has particular utility in designing machine tools to operate efficiently and effectively on workpieces consisting of all machinable metals. The invention embodies an effective means of cooling a machine tool at the interface between the cutting edge and the workpiece to reduce machining time and provide an acceptable end product.
2. Description of the Prior Art
The use of cutting fluids as a coolant for application to the cutting edge of a machine tool and/or the metal workpiece in order to increase the cutting rate and tool life, and to provide an acceptably finished workpiece is known in the art. One such prior art method is to flood the region of the machine tool cutting edge and workpiece with a coolant such as water soluble oil. The cooling effect of such a coolant, however, is often unacceptable. Further, this prior art method results in other disadvantages such as bad odor, water evaporation on the machine and tools leaving a scum surface thereon, and certain health and sanitary problems. The McLean U.S. Pat. No. 3,129,182 discloses the use as a cutting fluid of a mixture of a Freon and butyl Cellosolve in the machining of parts. The fluid is applied in a mist by simple spray and/or air jet application equipment which is external to the machine tool. An example of typical external equipment for this purpose is shown in West, Jr., U.S. Pat. No. 2,635,399 wherein a coolant such as carbon dioxide or other liquefied gas is externally directed in a stream toward the area of contact between the tool and an abrasive grinding surface.
The White U.S. Pat. No. 2,851,764 discloses an externally mounted source of a high pressure stream of cutting liquid which is forced by the ultrasonic alternating pressure present in the stream into contact with the tool cutting edge through the extremely small clearance between the tool and the workpiece to provide lubrication of the tool-chip interface. The White device uses a pump and a resonator chamber to cause the stream to strike the tool-chip interface with considerable force and requires rather complicated adjustment of the transducer system employed.
Benjamin U.S. Pat. No. 3,364,800 relates to a spade drill having means for creating a mist coolant adjacent the cutting edges thereof. The spade drill comprises several internally routed coolant tubes in the chuckhead through which coolant is directed. The internal passageways are specifically disclosed as having re-mister plugs for vaporizing any liquid-air mixture passing therethrough because the Benjamin device operates upon the basis that a mist coolant is able to penetrate into cutting areas not accessible by liquids. Thus Benjamin requires use of a spray mist and the precise aiming of the mist at the work/blade interface is not critical. The DuPont Bulletin No. FS-18 entitled "Freon T-B1 Cutting Fluid" illustrates a hollow drill for delivery of a spray mist comprising Freon, but cautions that this may be more effective than external delivery only in cases where chips are not an obstructing factor. Thus both this drill and the Benjamin drill do not solve the problem of cooling the interface between a machine tool and the workpiece when chips are an obstructing factor.